Bus signals comprise at least one signal line for a data signal and usually a signal line for a clock signal as well. The data signal and the clock signals have different purposes and have to be treated differently in order to decode the bus signal correctly.
When measuring a bus signal, the signal lines of the bus signal are connected to input channels of a signal analyzer for decoding the bus signal. For a correct measurement, it is important that the input channels are assigned, i.e. connected, correctly to the decoder, i.e. that the input channel receiving the data signal is assigned to a data input of the signal decoder and that the input channel receiving the clock signal, if present, is assigned to the clock input of the signal decoder.
This assignment is usually done by choosing the correct wiring manually, which is tedious and prone to errors.